Aqueous external crystal modifier dispersion

ABSTRACT

An aqueous external dispersion comprising a wax dispersant and an organic crystal modifier composition dispersed through a continuous water phase is useful as a crystal modifier for petroleum or a petroleum-derived liquid. The dispersant comprises a non-ionic surfactant and is present in the dispersion in an amount sufficient to impart at least meta-stability to the dispersion. The dispersion has a viscosity at 25° C. of less than about 50,000 centipoise.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to crystal modifiers, and moreparticularly to crystal modifiers useful as cold flow improvers, pourpoint depressants, viscosity reducers, paraffin deposition inhibitorsand the like for treatment of petroleum and petroleum-derived liquids.

2. Description of the Prior Art

Petroleum (crude oil) as it is produced from underground oil formationsoften is difficult to handle, particularly in cold weather. For example,it is common that paraffin deposition and/or increased viscosity or pourpoint render pumping difficult. Similarly, handling difficultiesfrequently persist in liquids derived from petroleum, such as automotiveoils, certain fuels and lubricating oil.

As a result, crystal modifiers are added to such liquids to improve thehandling characteristics. In relatively low concentration, the crystalmodifier may be used, for example, as cold flow improver or viscosityreducer to improve the flow of liquids such as petroleum and petroleumderived liquids at low temperature. In sufficient concentration, crystalmodifiers lower the pour point of the liquid and so often are termed"pour point depressants" in such situations. The crystal modifier alsomay prevent waxes (paraffin) from building up in production equipmentand thereby hindering operations.

Crystal modifiers interfere with crystal formation in fluids and so,depending on the fluid and situation, act as cold flow improvers, pourpoint depressants, viscosity reducers, paraffin deposition inhibitorsand the like. A variety of crystal modifiers are known in the art, andare generally identified by their function, such as cold flow improver,pour point depressant, viscosity reducer or paraffin depositioninhibitor. For example, the dialkylalkenylsuccinates of U.S. Pat. No.2,561,232 to Rudel et al. and assigned to Standard Oil DevelopmentCompany have been known as effective pour point depressants forpetroleum derived liquids since at least as early as 1951. U.S. Pat.Nos. 3,574,575 and 3,634,052, both of which were assigned to MobilCorp., and the text, Chemical Additives for Fuels: Developments Since1978, edited by M. T. Gillies (Noyes Data Corporation 1982), pages115-152, each of which is incorporated herein by reference, discloseother types of crystal modifiers. Recently, polymer compositionscomprising dispersions of at least one olefinically unsaturated compoundand containing aliphatic side chains of at least ten carbon atoms (e.g.,a polyacrylate or a polyethylene vinyl acetate related product), in acontinuous liquid phase comprising at least two surfactants and a liquidpolyol was disclosed anonymously in Research Disclosure (July 1995),page 501 (entry 37550), as being effective pour point depressants incrude oil (petroleum) and certain fuel oils. That disclosure calls forremoval of the organic solvents, dissolution in glycerin andemulsification in water so that the composition is nothydrocarbon-based.

Conventional crystal modifier technology, however, suffers from variousdrawbacks in treating petroleum and petroleum-derived liquids. Forinstance, the active ingredient of crystal modifiers often is a solid orhighly viscous liquid. Thus, the active ingredient suffers from the veryproblems it is intended to solve: it is difficult to handle; that is,removal of the crystal modifier from tanks, whether stationary or ontrucks, after storage or transport, and pumping of the crystal modifiersto the locus of treatment can be extremely difficult or impossible.

Therefore, conventional crystal modifier compositions often are lowconcentration mixtures or solutions of the active ingredient in asolvent, usually an aromatic hydrocarbon such as xylene bottoms. Ofcourse, this resolution in turn raises other disadvantages, includinghigher costs and difficulties attendant the purchase of large quantitiesof solvent and attendant the storage, transportation and application oflarge volumes of liquid for relatively low treatment rates. Moreover,the use of large quantities of solvent also increases the resultingamount of undesirable organic waste. In addition, if the additivecomposition is a dilute solution, it may have to be added continuouslyin order to afford continuous treatment. Because continuous treatmentrequires addition on-site equipment, operation and presence, it isdesirable that the composition be added by a batch application, withslow release of the active ingredient affording continuous treatment.

Attempts to respond to the problems encountered in diluting ordissolving the active crystal modifier in large volumes of solvent haveincluded the use of water-in-oil inverse emulsions such as disclosed inU.S. Pat. No. 5,027,901. The composition described in the ResearchDisclosure article identified above appears to be such a inverseemulsion. However, the reverse emulsions are still very viscous and sodo not resolve the handling problem to anywhere close to completesatisfaction. Further, as used conventionally, reverse emulsions havenot been known to provide a means for slow release of the activeingredient which could allow continuous treatment from a batchapplication. Moreover, such prior art compositions require undesirablyhigh flush rates for insertion downhole in oil wells.

SUMMARY OF THE INVENTION

The present invention, therefore, is directed to a novel aqueousexternal dispersion useful as a crystal modifier for petroleum or apetroleum-derived liquid. The dispersion comprises a wax dispersant andan organic crystal modifier composition dispersed through a continuouswater phase. The dispersant is present in the dispersion in an amountsufficient to impart at least meta-stability to the dispersion. Thedispersion has a viscosity at 25° C. of less than about 50,000centipoise.

The present invention is also directed to a novel method for crystalmodification of petroleum or a petroleum-derived liquid by adding thenoted aqueous external dispersion to the petroleum or petroleum-derivedliquid.

The present invention is further directed to a novel method for treatingan oil well for crystal modification of petroleum in the well. Accordingto the method, the noted aqueous external dispersion is injected intothe well annulus in a batch process and flushed into the well to adesired location for extended treatment.

The present invention is further directed to a novel method forpreparation of an aqueous external dispersion useful as a crystalmodifier for petroleum or a petroleum-derived liquid. According to themethod, a wax dispersant comprising a non-ionic surfactant and anorganic crystal modifier composition are combined and heated to form aliquid organic phase in which the dispersant is present in an amountsufficient to impart at least meta-stability to the resultingdispersion. Then, the organic phase is added to water at a rate ofaddition and with sufficient agitation and with the water at atemperature to disperse the organic phase throughout the water in anorganic phase weight average particle size of less than about 10microns. A dispersion comprising the dispersant and the organic crystalmodifier composition dispersed through a continuous water phase, andhaving a viscosity at 25° C. of less than about 50,000 centipoise, isthereby produced.

Among the several advantages of this invention, may be noted theprovision of a crystal modifier composition of suitably low viscosityfor ease of handling; the provision of a crystal modifier compositionthat requires lower flush rates than do prior art compositions forinsertion of the composition downhole in oil wells; the provision of acrystal modifier composition that contains lower amounts of aromatichydrocarbon solvents than many prior art compositions; the provision ofa crystal modifier composition that may be employed in a batchapplication that provides slow release of the active ingredient forcontinuous treatment over substantial periods of time; the provision ofa method for crystal modification of petroleum and petroleum-derivedliquids by application of a crystal modifier composition that is easierto handle than prior art compositions; the provision of such method thatproduces less aromatic hydrocarbon waste than prior art methods; theprovision of such method that involves a batch application resulting inrelatively long term continuous treatment; the provision of such methodthat is effective for treating an oil well for crystal modification ofpetroleum in the well; and the provision of a method for preparation ofsuch crystal modifier compositions useful in such methods.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, it has been discovered that arelatively low viscosity aqueous external dispersion comprising a waxdispersant and an organic crystal modifier composition dispersed througha continuous water phase can be prepared and used effectively forcrystal modification of petroleum or a petroleum-derived liquid. By"dispersion", what is meant is solid in liquid dispersions as well asliquid in liquid emulsions. By "crystal modification", what is meant iscold flow improvement, pour point depression, viscosity reduction and/orparaffin deposit inhibition. By "meta-stability", what is meant is thatthe discontinuous (organic) phase remains dispersed through thecontinuous (water) phase (i.e., less than about 10% of the waterseparates from the organic phase) for at least a week. Accordingly, thephrase "at least metastability" refers to such meta-stability or truestability. In general, the organic phase of the dispersions of thisinvention remain disperse for more than a month, usually more than threemonths, allowing it to be shipped and handled in a distribution system.However, once it is injected into a well annulus and flushed to thedesired point in the well, it releases the crystal modifier slowly,providing extended, continuous treatment.

Thus, the dispersion, which is an emulsion if the dispersed phase is aliquid rather than a solid, need not be prepared at the site of theapplication. The dispersion has a viscosity at 25° C. of less than about50,000 centipoise, typically about 5,000 to about 10,000 centipoise.Surprisingly, it has been found that this dispersion may be applied as abatch, yet it is of sufficiently low viscosity to render handling easyand to require relatively low flush rates for insertion into oil wells,and it releases the active ingredient at a relatively slow, constantrate to provide relatively long term continuous treatment.

The dispersion of this invention may be prepared as follows. A waxdispersant and an organic crystal modifier composition are combined toform an organic phase. By "wax dispersant", what is meant is asurfactant (or combination of surfactants) that disperses waxes orwax-like materials through an aqueous phase. In the case of a liquidcrystal modifier, therefore, the wax dispersant is a wax (or "waxy) inwater emulsifier. While the crystal modifier may not technically be awax, it is "waxy" in nature. It will be readily recognized by those ofordinary skill in the art the types of surfactants that are likely to beeffective dispersants in a particular oil in water system dependent, forexample, on the hydrocarbon solvent present.

Thus, for instance, the preferred dispersant comprises a non-ionicsurfactant and may, optionally, contain one or more other surfactants(ionic or non-ionic) as well. The preferred non-ionic surfactants aregenerally ethoxylated long hydrocarbon chain surfactants. By "longhydrocarbon chain", what is meant is eight or more, preferably twelve ormore, especially eighteen or more carbon atoms.

Alternatively, however, especially when the dispersed phase is a solid,the dispersant, may be a shorter chain ethoxylated hydrocarbonsurfactant (e.g., about six to about twelve carbon atoms) in combinationwith an ionic surfactant in a proportion such that the overalldispersant package (i.e., combination of surfactants/dispersants) has anHLB of about 6 to about 18, preferably about 6 to about 14, morepreferably about 8 to about 12, such as about 9 to about 11, especiallyabout 10, dependent, however, at least in part on the organic solvent,if any, present in the dispersion while an HLB of 10 is desirable ifxylene solvents are present in the dispersion, another HLB may bedesirable for another solvent such as kerosene. Appropriate HLB's for awide range of solvents are known. Thus, such non-ionic surfactants withrelatively shorter hydrocarbon chains, say six to twelve carbon atoms,tend to be suitable components for dispersants that also comprise ananionic surfactant such as dodecylbenzenesulfonic acid (DDBSA), whilenon-ionic surfactants of number average hydrocarbon chain lengths of atleast about eighteen carbon atoms, such as about twenty to thirty,especially about twenty-four to about twenty-eight carbon atoms, havebeen found to be especially useful if the dispersant contains no ionicsurfactant, particularly when the dispersed phase is a solid.

Preferred dispersants, particularly dispersants containing no surfactanthaving an ethoxylated hydrocarbon of chain of at least about eighteencarbon atoms, have a hydrophilic/lipophilic balance (HLB) of from about6 to about 18, preferably from about 6 to about 14, more preferably fromabout 8 to about 12, such as from about 9 to about 11, preferably about10, dependent, however, at least in part on the organic solvent, if any,present in the dispersion. If the dispersant contains a combination ofsurfactants, the HLB of the dispersant is considered herein to be theweight average of the HLB's of the individual surfactants. Those ofordinary skill in the art will readily recognize or determine thedispersants likely to be most effective for the particular system. Whena solvent (e.g., a hydrocarbon) is present, the type of dispersant(surfactant) can be determined from the type of solvent. For example,HLB's suitable for various solvents in oil in water emulsions are wellknown and published, for instance, in The HLB System, by ICI Americas,Inc. (1976).

In view of these constraints, a particularly effective non-ionicsurfactant, especially if used as the sole surfactant, has been found tobe hydroxylated polymerized ethylene with a chain length distribution inthe range of from about eight to about sixty carbon atoms, preferablyabout twelve to about forty carbon atoms, more preferably about eighteento about forty carbon atoms, with a number average, for example, of fromabout twenty to about fifty carbon atoms, preferably about twenty toabout thirty carbon atoms, more preferably about twenty-four to abouttwenty-eight carbon atoms, such as about twenty-four to about twenty-sixcarbon atoms. One suitable polymer that may be noted is an aliphaticalcohol having a number average backbone length of about 24 to about 26carbon atoms ethoxylated with ethylene oxide in a weight ratio ofethylene oxide to the backbone of from about 1:0.5 to about 1:2,preferably approximately 1:1.

Non-ionic surfactants that have been found effective in combination withan anionic surfactant such as DDBSA include ethoxylated nonylphenol (4:1molar ratio of ethylene oxide to nonylphenol) and an ethoxylated C₁₂₋₁₃alkyl backbone (3:1 molar ratio of ethylene oxide to alkylate) such asis available from Shell under the trade designation Neodol 23-3. In suchcombinations, the relative amounts of non-ionic surfactant and DDBSAshould be coordinated so that the HLB of the dispersant is about 6 toabout 18, preferably about 6 to about 14, more preferably about 8 toabout 12, especially about 9 to about 11, such as about 10.

In any event, the dispersant is coordinated with the system as will bereadily seen by the ordinarily skilled artisan in the field of emulsionsand dispersions. The dispersant and its concentration are selected tocause the oil phase to disperse through the water phase to achieve atleast meta-stability. Generally, the dispersant concentration in theoverall dispersions will be about 1% to about 15% by weight, dependingon the dispersant, the oil phase and the ratio of oil to water.

It is believed that the organic crystal modifier composition maycomprise any known crystal modifier useful for improving the cold flowof, depressing the pour point of, reducing the viscosity of, orinhibiting paraffin deposition in, petroleum and petroleum-derivedliquids. Especially suitable crystal modifiers perform more than one ofthese functions and may also perform other functions as well, such ascorrosion inhibition.

Particular crystal modifiers that have been found specifically to besuitable include those of the U.S. patents and the text that areidentified in the Background section above and incorporated herein byreference. However, especially effective crystal modifiers in thisinvention are olefin/maleic anhydride copolymers, particularlyα-olefin/maleic anhydride copolymers, whether in their acid, diacid,ester, diester, ester/acid, amide, imide or anhydride forms, or in acombination of forms, also have been found to be especially effective inthis invention. Other types of crystal modifiers, including ethylenevinyl acetate copolymers (number average molecular weight of generallyup to about 10,000), polyacrylates, and esters amides and imidesthereof, are well known in the field as such or more specifically ascold flow improvers, pour point depressants, viscosity reducers orparaffin inhibitors. Generally, polymeric crystal modifiers have aweight average molecular weight of about 3,000 to about 10,000,preferably about 5,000 to about 10,000. Nevertheless, other crystalmodifiers may be used, for example, crystal modifiers of U.S. Pat. No.2,561,232 are aliphatic alcohol diesters of an alkenylsuccinic acidcontaining a single alkenyl group of 4 to 24 carbon atoms, in which thealcohol radicals are alkyl groups of 2 to 14 carbon atoms or alkoxyradicals of the type C₄ H₉ (OCH₂ CH₂)_(n) OH, wherein n is 1 or 2. Suchcrystal modifiers may be used in the dispersions of this invention.Suitable ester crystal modifiers include aliphatic alcohol esters andhave up to thirty carbon atoms, preferably about eighteen to aboutthirty carbon atoms, especially about twenty to about twenty-eightcarbon atoms.

Thus, for example, the crystal modifier may be a polymeric ester such asa C₃₀ alpha olefin/maleic anhydride copolymer (an alternating copolymerof number average molecular weight about 5,000) 75 mole % esterifiedwith C₂₀₊ alcohols. Or it may be an imide derived from that polymer. Inparticular, an imide (of weight average molecular weight of 5,000)prepared by reacting a C₂₄₋₂₈ alpha olefin/maleic anhydride copolymerwith ARMEEN HT (a hydrogenated tallow amine) has been found to be aneffective cold flow improver/pour point depressant/viscosityreducer/paraffin inhibitor. Thus, by these and similar techniques, thepolymers may be used not only in its anhydride, acid and diacid forms,but also in its ester, diester, acid/ester, amide and imide forms,including mixtures of such forms. Or the crystal modifier may be apolyacrylate as described in the Research Disclosure article noted aboveand incorporated herein by reference.

Generally the crystal modifier composition of this invention is acrystal modifier (or a combination of crystal modifiers) in an organicsolvent, such as an aromatic solvent, especially an aromatic hydrocarbonsuch as xylene bottoms (mostly mesitylenes), kerosene, diesel fuel,naphthalenes and other heavy aromatics. However, whereas in prior artcompositions, the crystal modifier is dissolved or dispersed in anaromatic typically in very low concentration in an effort to prepare acomposition that can be handled, in the present invention the crystalmodifier composition is dispersed through water, eliminating the needfor much of the aromatics employed in the prior art techniques. Thus,crystal modifier compositions ranging from 3% active (that is, 3% byweight of the combination crystal modifier(s) and organic solvent is thecrystal modifier(s)) to 87% active. Generally, use of crystal modifiercompositions at least about 10% active, preferably at least about 20%active, especially about 20% to about 90% active, such as about 20% toabout 60% active, have been found to result in highly desirabledispersions.

The dispersion may also comprise other ingredients that can impartadditional properties to the dispersion. For example, the dispersion mayinclude a scale inhibitor, a corrosion inhibitor, or a bactericide, solong as the ingredient does not de-stabilize or break the dispersion. Infact, however, it has been found that certain imidazoline corrosioninhibitors act as emulsifying or dispersing aids; that is, not only dothey inhibit corrosion, but they help stabilize the dispersion.Exemplary of such imidazoline corrosion inhibitors are reaction productsof tall oil fatty acid with diethylenetriamine or fatty aminecondensates generally. Such imidazoline corrosion inhibitors aredisclosed in U.S. Pat. Nos. 4,746,328, 5,062,992, 5,152,177, 5,504,063and 5,459,125, each of which is incorporated herein by reference. Othercorrosion inhibitors, such as fatty acid derivatives (e.g., dimer acidsand trimer acids) have been found to be useful as well. These additionalingredients are preferably oil soluble.

The dispersions of this invention may be produced as follows. An organicphase is prepared by adding the dispersant to the crystal modifiercomposition, typically with heat to facilitate dissolution of thedispersant in the crystal modifier composition. Or, if the organic phaseis a solid at ambient temperature, it is heated to maintain it in liquidform. The relative amounts should be such that the dispersant will bepresent in the ultimate dispersion in an amount sufficient to impart atleast meta-stability to the dispersion. Generally, this concentration isabout 2 to about 10 weight percent based on the total resultingdispersion. If the dispersion is to contain any other organic phasecomponents, such as a scale inhibitor, a corrosion inhibitor, a freezingpoint depressant, an asphaltene inhibitor, or a bactericide, they arealso added to the organic phase at this point.

The organic phase is then added to water at a rate and with sufficientagitation--and with the water maintained at a sufficient temperature(usually near boiling)--to disperse the organic phase throughout thewater in an organic phase weight average particle size of at most about50 microns, preferably up to about 25 microns, more preferably up toabout 10 microns, especially up to about 7 microns, such as up to about5 microns. These sizes refer to the size sieve opening through which theparticles can pass. Those of ordinary skill in the art will readilyrecognize how to control these factors to achieve the dispersion andwill be able to adapt and to coordinate them for particular formulationswithout undue experimentation. Preferably, the organic phase is added tothe water in a proportion such that the resulting crystal modifierconcentration in the dispersion is from about 10 to about 70% by weight,more preferably about 10 to about 50% by weight, most preferably about20 to about 40% by weight. In a preferred embodiment, if the crystalmodifier is dissolved in an aromatic hydrocarbon solvent, the dispersioncontains up to about 50% by weight aromatic hydrocarbon solvent.Generally, the dispersions are at least of 25% by weight water. Thedispersant is typically dispersed in the water phase and around or inthe organic phase.

The resulting dispersion comprises the dispersant and the organiccrystal modifier composition dispersed through a continuous water phase,the dispersion having a viscosity at 25° C. of less than about 50,000centipoise, preferably about 5,000 centipoise to about 15,000centipoise. For dispersions intended to be used to treathydrocarbon/water mixtures, the dispersion generally has a densitybetween that of water and the hydrocarbon in the fluid being treated. Itmay then tend to locate at the interface between the water and thehydrocarbon. Thus, the density is less than 1 gm./cm³ and greater thanthe petroleum or petroleum-derived liquid. For example, if the liquid iscrude oil, which has a density generally from about 0.75 to about 0.96gm./cm³, the density of the dispersion should be between at least about0.75 and about 1 gm./cm³, depending on the density of the actual crudebeing treated, but more typically from about 0.85 to about 1 gm./cm³,preferably from about 0.9 to about 1 gm./cm³, especially from about 0.96to about 1 gm./cm³, such as about 0.97 gm./cm³, depending on the densityof the particular crude oil.

The dispersion may be applied to the petroleum or petroleum-derivedfluid by a batch application. For example, if added to an oil well, acharge of the dispersion is added as a batch through the annulus of thewell and then flushed to the desired location downhole with brine orproduction fluid. The dispersion is particularly well suited foroff-shore use due to its physical properties of high concentration, easeof handling, multifunctionality, and so forth. The amount to be addedwill vary from well to well. This will be readily recognized by those ofordinary skill in the art, as will suitable amounts for addition. Thedispersion then releases the crystal modifier continuously over anextended period, and formulations can be prepared, for example, torelease about 50 to about 100 ppm active crystal modifier for weeks ormonths before a new charge of dispersion is required. Similarly theother active ingredients incorporated into the dispersion may bereleased slowly for continuous treatment. Thus, whereas traditionalbatch treatments of wells involves batch additions and prompt return ofthe additive with production, thereby requiring constant retreatment,the batch addition of the composition of this invention permits acontinuous treatment over an extended period of time.

The following examples describe preferred embodiments of the invention.Other embodiments within the scope of the claims herein will be apparentto one skilled in the art from consideration of the specification orpractice of the invention as disclosed herein. It is intended that thespecification, together with the examples, be considered exemplary only,with the scope and spirit of the invention being indicated by the claimswhich follow the examples. In the examples, all percentages are given ona weight basis unless otherwise indicated.

EXAMPLE 1

Several crystal modifier compositions were prepared and their meltingpoints measured. First, an ester composition corresponding to an 87% byweight mixture of C₃₀ alpha olefin/maleic anhydride alternatingcopolymer (number average molecular weight about 5,000) that has been 75mole % esterified with C₂₀₊ alcohols dissolved in xylene bottoms (highmesitylene content) was prepared. It was found to have an approximatemelting point of 135° F. (about 57° C.). The ester was diluted furtherwith more of the xylene bottoms to form a 54% active mixture having anapproximate melting point of 105° F. (about 41° C.), and diluted evenfurther to form a 3% active mixture having an approximate melting pointof 25° F. (about -4° C.). A 21% mixture of the imide reaction product ofC₂₄₋₂₈ alpha olefin/maleic anhydride copolymer (molecular weight about5,000) and Armeen HT (hydrogenated tallow amine) in xylene bottoms wasprepared and found to have an approximate melting point of 35° F. (about2° C.). Finally, a mixture was prepared containing 18% of the notedester and 5% of the noted imide in xylene bottoms (for a total activeconcentration of 23%) and found to have an approximate pour point of 40°F. (about 4° C.).

EXAMPLE 2

A dispersion of this invention was prepared as follows. Distilled waterwas heated to 200°-205° F. (about 95° C.) and held at that temperature.An 87% by weight solution of C₃₀ alpha olefin/maleic anhydride copolymer(number average molecular weight about 5,000) that has been 75 mole %esterified with C₂₀₊ alcohols (as disclosed in U.S. Pat. No. 2,561,232to Rudel et al. and assigned to Standard Oil) dissolved in xylenebottoms (high mesitylene content) was heated to 240°-250° F. (about 120°C.) and maintained at 245° F. (about 118° C.). A 90% solution ofimidazoline corrosion inhibitor (sold by Petrolite Corporation under thetrade designation CRO-111) was added slowly to the hot olefin/maleicanhydride copolymer ester solution with agitation in a weight ratio ofabout 13:29 (an active weight ratio of about 10:21). The temperature ofthe resulting ester/corrosion inhibitor mixture was maintained at 245°F. (about 118° C.) and held there for five minutes beyond the completionof the addition. A 25% solution of the imide reaction product of C₂₄₋₂₈alpha olefin/maleic anhydride copolymer (molecular weight about 5,000)and Armeen HT (hydrogenated tallow amine), was then added to theester/corrosion inhibitor mixture at 245° F. (about 118° C.) in a weightratio of about 8:13 and the resulting imide/ester/corrosion inhibitormixture was then held at that temperature for five minutes. Anethoxylated aliphatic compound of approximately forty carbon atoms andhaving a backbone of about 24 to about 26 carbon atoms ethoxylated withethylene oxide in a weight ratio of ethylene oxide to the backbone ofapproximately 1:1 (number average molecular weight about 900; HLB=10)was then added to the imide/ester/corrosion inhibitor mixture at 245° F.(about 118° C.) in a weight ratio of about 3:35 and the resultingmixture was stirred until all ingredients were melted and well mixed.The melted, stirred mixture was then added slowly to the hot distilledwater in a weight ratio of about 8:7. Significant agitation and atemperature of about 205° F. (about 96° C.) were maintained during theaddition and for 3 to 5 minutes thereafter. The product was then cooledat a rate of about 3° to 50° F. (about 11/2 to about 3° C.) per minutewith mild agitation until the product reached 100° F. (about 38° C.).

EXAMPLE 3

A well was treated on days 1 and 20 with the product prepared asdescribed in Example 2, above (10 gallons per treatment), by batchaddition of the product, followed by flushing. The pour point of thewell fluid was measured, with the following results:

    ______________________________________                 POUR                 POINT            DAY  (°F.)    ______________________________________            1    *42            2    <0            3    20            4    30            5    26            6    30            7    28            8    32            9    32            10   26            11   26            12   26            13   30            14   30            15   23            16   22            17   24            18   20            19   20            20   14            22   10            23   6    ______________________________________     *(prior to treatment)

EXAMPLE 4

Crudes obtain from several wells were treated for paraffin depostioninhibition with various concentrations of the prepared as described inExample 2. The weight % of the paraffin deposition inhibited wasmeasured for each crude for each of the crystal modifier concentrations,with the following results: was measured for each crude for each of thecrystal modified concentrations, with the following results:

    ______________________________________    Crystal Modifier    Concentration  Paraffin Deposition    (ppm by weight)                   Inhibition (wgt. %)    ______________________________________    Crude #1    50             43    100            33    200            61    300            81    400            83    Crude #2    126            22    252            35    504            82    756            65    1008           55    Crude #3    125            94    250            97    500            85    750            98    Crude #4    125            73    250            91    500            95    750            97    ______________________________________

In view of the above, it will be seen that the several advantages of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above methods and compositionswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

What is claimed is:
 1. An aqueous external dispersion useful as acrystal modifier for petroleum or a petroleum-derived liquid, comprisinga wax dispersant and an organic crystal modifier composition dispersedthrough a continuous water phase, the crystal modifier compositioncomprising a crystal modifier or combination of crystal modifiers andthe crystal modifier or combination of crystal modifiers makes up about10% by weight to about 70% by weight of the dispersion, the waxdispersant being present in the dispersion in an amount sufficient toimpart at least meta-stability to the dispersion, and the dispersionhaving a viscosity at 25° C. of less than about 50,000 centipoise.
 2. Anaqueous external dispersion as set forth in claim 1 wherein thedispersion has a viscosity at 25° C. of from about 5,000 centipoise toabout 15,000 centipoise.
 3. An aqueous external dispersion as set forthin claim 1 having a density less than 1 gm./cm³ and greater than thepetroleum or petroleum-derived liquid.
 4. An aqueous external dispersionas set forth in claim 3 having a density greater than about 0.75gm./cm³.
 5. An aqueous external dispersion as set forth in claim 1wherein the dispersant comprises a non-ionic surfactant selected fromthe group consisting of ethoxylated hydrocarbons having a carbon chainof at least about eighteen carbon atoms in length and ethoxylatedhydrocarbons of shorter chain length, provided however that if thenon-ionic surfactant is an ethoxylated hydrocarbon of shorter chainlength, the dispersant further comprises an ionic surfactant in anamount such that the dispersant has an HLB of from about 6 to about 18.6. An aqueous external dispersion as set forth in claim 1 wherein thedispersant is an ethoxylated aliphatic alcohol having a backbone ofnumber average length of about 20 to about 50 carbon atoms ethoxylatedwith ethylene oxide in a weight ratio of ethylene oxide to the backboneof approximately 1:0.5 to approximately 1:2.
 7. An aqueous externaldispersion as set forth in claim 5 wherein the dispersant is acombination of (a) nonylphenol ethoxylated in an ethylene oxide tononylphenol molar ratio of approximately 4:1, and (b)dodecylbenzylsulfonic acid, in a proportion of (a) to (b) sufficient toproduce an HLB of the combination of about 6 to about
 18. 8. An aqueousexternal dispersion as set forth in claim 5 wherein the dispersant is anon-ionic ethoxylated hydrocarbon surfactant having a carbon chain of atleast about eighteen carbon atoms in length.
 9. An aqueous externaldispersion as set forth in claim 1 wherein the organic crystal modifiercomposition comprises an olefin/maleic anhydride copolymer having weightaverage molecular weight of from about 3,000 to about 10,000.
 10. Anaqueous external dispersion as set forth in claim 9 wherein thecopolymer is of an acid, diacid, ester, diester, acid/ester, anhydride,amide or imide form, or a combination thereof.
 11. An aqueous externaldispersion as set forth in claim 10 wherein the organic crystal modifiercomposition further comprises an aromatic hydrocarbon solvent.
 12. Anaqueous external dispersion as set forth in claim 1 wherein the organiccrystal modifier composition comprises an olefin/maleic anhydridecopolymer having weight average molecular weight of from about 3,000 toabout 10,000.
 13. An aqueous external dispersion as set forth in claim 9wherein the crystal modifier is also a paraffin deposition inhibitor.14. An aqueous external dispersion as set forth in claim 1 wherein theorganic crystal modifier composition is dispersed in the form ofparticles having a weight average particle size of up to about 50microns.
 15. An aqueous external dispersion as set forth in claim 1further comprising at least one other agent selected from the groupconsisting of oil soluble corrosion inhibitors, scale inhibitors,asphaltene inhibitors, bactericides and freezing point depressants. 16.An aqueous external dispersion as set forth in claim 11 wherein thedispersion contains from 0 to about 50% aromatic hydrocarbon solvent.17. A method for crystal modification of petroleum or apetroleum-derived liquid, comprising adding to the petroleum orpetroleum-derived liquid an aqueous external dispersion as set forth inclaim
 1. 18. A method as set forth in claim 17 wherein the dispersion isadded to the petroleum or petroleum-derived liquid as a batch treatmentand the dispersion releases the crystal modifier composition to thepetroleum or petroleum-derived liquid continuously over an extendedperiod of time.
 19. A method as set forth in claim 17 wherein thedispersion has a viscosity at 25° C. of from about 5,000 centipoise toabout 15,000 centipoise.
 20. An aqueous external dispersion as set forthin claim 17 having a density less than 1 gm./cm³ and greater than thepetroleum or petroleum-derived liquid.
 21. An aqueous externaldispersion as set forth in claim 17 wherein the dispersant is acombination of surfactants.
 22. An aqueous external dispersion as setforth in claim 17 wherein the dispersant is an ethoxylated aliphaticcompound having a backbone number average length of about 20 to about 50carbon atoms ethoxylated with ethylene oxide in a weight ratio ofethylene oxide to the backbone of approximately 1:0.5 to approximately1:2.
 23. An aqueous external dispersion as set forth in claim 21 whereinthe dispersant is a combination of (a) nonylphenol ethoxylated in anethylene oxide to nonylphenol molar ratio of approximately 4:1, and (b)dodecylbenzylsulfonic acid, in a proportion of (a) to (b) sufficient toproduce an HLB of the combination of about 6 to about
 18. 24. An aqueousexternal dispersion as set forth in claim 17 wherein the organic crystalmodifier composition comprises an olefin/maleic anhydride copolymerhaving weight average molecular weight of from about 3,000 to about10,000.
 25. An aqueous external dispersion as set forth in claim 24wherein the copolymer is of an acid, diacid, ester, diester, acid/ester,anhydride, amide or imide form, or a combination thereof.
 26. An aqueousexternal dispersion as set forth in claim 25 wherein the organic crystalmodifier composition further comprises an aromatic hydrocarbon solvent.27. An aqueous external dispersion as set forth in claim 26 wherein thedispersant comprises a non-ionic surfactant selected from the groupconsisting of ethoxylated hydrocarbons having a carbon chain of at leastabout eighteen carbon atoms in length and ethoxylated hydrocarbons ofshorter chain length, provided however that if the non-ionic surfactantis an ethoxylated hydrocarbon of shorter chain length, the dispersantfurther comprises an ionic surfactant in an amount such that thedispersant has an HLB of from about 6 to
 18. 28. An aqueous externaldispersion as set forth in claim 24 wherein the crystal modifier is alsoa paraffin deposition inhibitor.
 29. An aqueous external dispersion asset forth in claim 17 wherein the organic crystal modifier compositionis dispersed in the form of particles having a weight average particlesize of up to about 50 microns.
 30. An aqueous external dispersion asset forth in claim 17 further comprising at least one other agentselected from the group consisting of oil soluble corrosion inhibitors,scale inhibitors, bactericides, asphaltene inhibitors and freezing pointdepressants.
 31. An aqueous external dispersion as set forth in claim 26wherein the dispersion contains from 0 to about 50% aromatic hydrocarbonsolvent.
 32. A method for preparation of an aqueous external dispersionuseful as a crystal modifier for petroleum or a petroleum-derivedliquid, comprising:combining and heating a wax dispersant and an organiccrystal modifier composition to form an organic phase, the dispersantcomprising a non-ionic surfactant, to form a liquid organic phase; andthen adding the liquid organic phase to water at a rate of addition andwith sufficient agitation and with the water at a temperature todisperse the organic phase throughout the water in an organic phaseweight average particle size of less than about 10 microns; thereby toproduce a dispersion comprising the dispersant and the organic crystalmodifier composition dispersed through a continuous water phase, thecrystal modifier composition comprising a crystal modifier orcombination crystal modifiers and the crystal modifier or combination ofcrystal modifiers makes up about 10% by weight to about 70% by weight ofthe dispersion, the dispersion containing at least 25% by weight waterand having a viscosity at 25° C. of less than about 50,000 centipoise.33. An aqueous external dispersion as set forth in claim 1 wherein thecrystal modifier composition comprises a crystal modifier or combinationof crystal modifiers and the crystal modifier or combination of crystalmodifiers makes up about 20% by weight to about 40% by weight of thedispersion.
 34. An aqueous external dispersion as set forth in claim 1wherein water makes up at least about 25% by weight of the dispersion.35. A method as set forth in claim 17 wherein the crystal modifiercomposition comprises a crystal modifier or combination of crystalmodifiers and the crystal modifier or combination of crystal modifiersmakes up about 20% by weight to about 40% by weight of the dispersion.36. A method as set forth in claim 17 wherein water makes up at leastabout 25% by weight of the dispersion.